Method for determining bran in cereal flour



UNITED STAT Patented June 23, 1953 METHOD FOR DETERMINING BRAN IN CEREALFLOUR Roger A. Larkin, Peoria, 111., assignor to the United States ofAmerica as represented by the Secretary of Agriculture NoDrawing.Application July 8, 1952,

v Serial No. 297,800

'IClaims. (o1. 73-432) (Granted under A non-exclusive, irrevocable,royalty-free license in the invention, herein described, for allgovernmental purposes, throughout the world, with the power to grantsublicenses for such purthe United States of America.

in wheat flour.

a simple dye technique.

flours.

significance.

somewhat empirical in character.

not stain the endosperm cell walls.

the base.

of the solid residue.

may also be present in the solid residue are color- Title 35, U. S. Code(1952),

see. 266) less. The alkali treatment produces a differentialdecolorization, and the decolorizing action is stopped at a point beforebran and germ particles have been decolorized and after the other Forexample, it

poses, is hereby granted to the Government of materials in the mixturehave become colorless.

The bran and germ content of the flour sam- The invention relates to amethod for deterple may be determined visually, i. e., by estimatminingthe presence of bran and germ particles ng the relative proportion, bycountin the It relates, particularly, to. a fragments, or by any othervisual method as method for determining such particles in cerealdesired. flour or in similar comminuted compositions by The inventionpossesses several advantages As will be explained in over priorevaluating methods. detail below, the method is more accurate and doesnot depend upon a gravimetric or other definitive than prior methods forevaluating kind of chemical analysis. It maybe carried out a inconsiderably less than 2 hours time, requires The degree of refinementof a cereal flour may o special equipment, except a microscope, and bemeasured by the completeness of theseparadoes not require highly trainedpersonnel. tion of the bran and germ constituents from the The followingprocedure is a preferred method endosperm and resultant flour.Evaluation of of carrying out the in ti flours to determine the degreeof refinement'has 0 1. A Wei e a p e of f o iS Wet with ethlong been aproblem of considerable economic anol, preferably 95 percent ethanol.

Prior methods have frequently in- 2. Crystal Violet dye is applied inthe form of volved such indirect determinations as ash con- 0.04 to 0.07percent aqueous solution. Suflicient tent, color tests, or combinationsof both. Pentodye should be added to form a watery suspension .sancontent has also been suggested as a test. or at least a thin slurry.

The prior methods of evaluation have required 3. After permitting thedye mixture to stand complicated and rather tedious techniques and forabout 10 minutes. sufllcient 0.25 N sodium have not providedsatisfactory criteria, all being hydtroxide is added to disperse thestarch and pro em. It has been discovered, in accordancewith this Afterstanding for about 5 minutes, an invention, that Crystal Violet dye whenapplied app ately equal volume'of distilled water is to a flour samplestains-the germ and the bran added, and the mixture stirred and letstand for layers and protein of the endosperm, but does about 1 hour.

Such a dyed 5. The mixture sample may be treated with a strong base such1, white filter paper. I as sodium hydroxide or potassium hydroxide inThe bran and germ particles appear violet in aqueous solution to leave,the bran and germ color upon the white filter paper. Other matefragmentsstained distinctively, the remainder rial on the paper which may beminor amounts of the sample having been rendered colorless by f e permcell walls, incompletely dispersed 40 starch, vor incompletely dispersedprotein are Utilizingthese discoveries, a simple procedure colorless.Bran and germ particles are, therehas been developed which affords arapid and fore, easily identified, and the deposited matereliabledetermination of the bran and germ conrial maybe observed wet or dry.The detertent of cereal flours or of cereal flour mixtures, m ati may beConveniently accomplished Visor even of baked or otherwise finished foodprodually. It may also be accomplished directly or ucts consistingmainly of flour. Intgene'ral, the indirectly by light transmittance,reflectance, method comprises applying a dilute aqueous solucolorimetricmethods or similar methods familiar tion of the dye to the sample,subsequent treatto skilled workers. For example, light reflected mentwith aqueous alkali andthen separation of from a stained sample may bemeasured and the liquid medium followed by final observance 5O corded byphotoelectric devices as an indication Ihe bran and germ parof the brancontent. ticles, after this treatment, app Violet in Slight variationsin the timing of various steps or. Endosperm cell walls, incompletelydispersed do not affect the result, and the procedure can be starch andincompletely dispersed protein which completed in about 1 hours. Thetime may be shortened by permitting the alkali to act for is filtered,preferably using about minutes in the third step, then adding thedistilled water and filtering immediately. This variation in proceduremust be timed fairly accurately, lest the action of the alkali cause thegerm and bran particles to become decolorized.

A useful variation of the invention can be em.- ployed to show theendosperm cell walls in wheat fiour. Approximately 30 minutes'afterthewater has been added in the fourth step, one ml. of about 0.1 percentaqueous Congo red stain is added to the mixture. sperm cell wallparticles an orange red. 'The sample should be examined in the stainingsolution. It is not practical to combine the two determinations on thesame sample, howeven'ior the bran and germ particles tend to stainorange red after contact with the Congo red for to minutes. Moreover,the filtration with filter paper tends to interfere with the resultsbecause the red dye stains the filter paper.

Observation of the violet stained bran and germ particles is preferablycarried out microscopically. Both appear about the same under lowmagnification, but under high magnification, say of about 100X, the branparticles usually appear as fiat pieces, while the germ particles appearas small, irregularly-shaped thick pieces. The evaluation is notabsolute, however, for it is difiicult to distinguish between very smallparticles of bran and of germ. f

The following specific example illustrates the invention.

Example One-gram samples each of patent, first clears and red dog flourwere wetted with 95 percent ethyl alcohol. Each sample wasthen mixedwith 18 ml. of 0.05 percent Crystal Violet and let stand for 10 minutes.Each was then mixed with 120 ml. of 1.0 percent (025 N) sodium hydroxideand let stand for five minutes, whereupon 140 ml. of distilled water wasadded and'the mixture let stand for one hour. The mixture was thenfiltered on No. 1 Whatman filter paper, using a coarse fritted glassfunnel.

The filter paper obtained from the red dog sample had a deep violetappearance. Microscopic examination revealed'that the color was due tosmall particles of bran that had been dyed. The filter paper from thefirst clears sample was an intermediate shade of violet with a finelymottled appearance, the color being due to the presence of aconsiderable amount of dyed bran. The filter paper obtained from thepatent sample had an overall tint of light violet, caused by individualparticles of dyed bran peppered over the paper.

The number of steps set forth above represent preferred procedure.However, it is to be understood that the invention may be carried out ina wide variety of ways. The concentration of Crystal Violet dye must bekept within the designated limits.

Wetting the sample with ethanol or other denaturing agent is usuallynecessary for satisfactory results, for it prevents pasting andfacilitates contact between the dye solution and the sample. It is onlynecessary that contact between the sample and the dye be sufiicientlylong to afford full staining. The amount of sodium hydroxide, or otheralkali, may be increased or decreased compared with that specified inthe numbered steps. However, the more alkali present, and the strongerit is, the faster the decolorization This stains the endoprocess willbe, and it is desirable that decolorization proceed at a rate slowenough to effect substantial decolorization of all substances presentexcept the bran and germ particles.

I claim:

1. A method for determining bran and germ particle constituents incereal flours comprising treating a given samle of flour material with a0.04-0.07 percent aqueous solution of Crystal Violet whereby to dye branand germ particles present in said fiour material together with othermaterial present, effecting differential decolorizing by treating themixture with an aqueous solution of alkali until substantially all otherconstituents are decolorized, separating the solid material from theresulting alkaline solution and subsequently determining the amount ofbran and germ particle constituents.

2. A method for determining bran and germ particle constituents incereal flours comprising treating a given sample of flour materialcontaining bran and germ particle constituents with a 0.04-0.07 percentaqueous solution of Crystal Violet whereby to dye at least said bran andgerm constituents, treating said dye mixture with aqueous alkali todecolorize and substantially disperse the protein and starchconstituents of said flour and separating the solid constituents fromthe alkaline aqueous solution before the bran and germ constituentsbecome decolorized and subsequently determining the amount of bran andgerm constituents.

3. The method comprising wetting a known quantity of cereal flour inaqueous ethanol, adding sufiicient 0.04-0.07 percent aqueous solution ofCrystal Violet to color the constituents of said cereal fiour, addingalkali in sufficient quantity to decolorize differentially the starch,protein and endosperm cell wall material with respect to the bran andgerm constituents and subsequently separating the colored bran and germconstituents from the aqueous dye solution before said bran and germconstituents undergo substantial decolorizing, and subsequentlydetermining the content of bran and germ constituents by visualobservation.

4. The method of claim 1 in which the treatment with aqueous alkali iscarried out using 1.0 percent sodium hydroxide.

5. Method of claim 4 in which the alkaline treatment period is about 5minutes and is followed by dilution of the mixture with about an equalvolume of water and the diluted mixture permitted to stand for about 1hour before separation of the insoluble constituents.

6. Method of claim t in which the alkaline treatment period isapproximately 15 minutes followed substantially immediately by dilutionwith about an equal volume of water.

7. The method of rendering bran and germ particles, derived from cerealgrains, visually distinguishable from other components of said cerealgrains comprising subjecting a mixture of said particles and said othercomponents to the action of a 0.04-0.07 percent aqueous solution ofCrystal Violet dye followed by alkaline decolorization of said othercomponents.

ROGER A. LARKIN.

References Cited in the file of this patent UNITED STATES PATENTS Number

1. A METHOD FOR DETERMINED BRAN AND GERM PARTICLE CONSTITUENTS IN CEREALFLOURS COMPRISING TREATING A GIVEN SAMLE OF FLOUR MATERIAL WITH A0.04-0.07 PERCENT AQUEOUS SOLUTION OF CRYSTAL VIOLET WHEREBY TO DYE BRANAND GERM PARTICLES PRESENT IN SAID FLOUR MATERIAL TOGETHER WITH OTHERMATERIAL PRESENT, EFFECTING DIFFERENTIAL DECOLORIZING BY TREATING THEMIXTURE WITH AN AQUEOUS SOLUTION OF ALKALI UNTIL SUBSTANTIALLY ALL OTHERCONSTITUENTS ARE DECOLORIZED, SEPARATING THE SOLID MATERIAL FROM THERESULTING ALKALINE SOLUTION AND SUBSEQUENTLY DETERMINING THE AMOUNT OFBRAN AND GERM PARTICLE CONSTITUENTS.